1. Field
The method and apparatus are directed generally to using multiple signal source types to determine location, and more particularly to using multiple signals source types to increase accuracy of a location determination and/or reduce power usage therewith, and/or shortening time required to make a location determination.
2. Related Art
There currently exist a number of location determination methods and apparatuses. None of these methods and apparatuses is necessarily perfect or operates in all situations. There is typically a trade-off between accuracy, power consumption, sensitivity, and cost.
For example, one common system is the Global Positioning System (GPS). The GPS system is a global navigation satellite system. It utilizes a constellation of medium earth orbit satellites that transmit precise microwave signals. These signals allow a GPS receiver to determine a position location, for example by triangulation.
GPS signals typically are transmitted at a particular frequency (about 1.575 GHz). Such a frequency may be strongly attenuated by buildings and other man made structures, or have a tendency to be affected by multi-path signals created by an urban environment or affected by inconsistencies in atmospheric conditions, for example. Accordingly, suitable GPS signals may not be always available to a GPS receiver.
Various attempts have been made to create alternatives that overcome the disadvantages of the GPS system, for example location determination employing digital television transmitters, cell phone base stations, Wi-Fi or Wi Max access points and the like. Signals from other transmitters may also not be optimal.